Associations of LBX1 gene and adolescent idiopathic scoliosis susceptibility: a meta-analysis based on 34,626 subjects

Genetic animal modeling for idiopathic scoliosis research: history and considerations

PURPOSE

Idiopathic scoliosis (IS) is defined as a structural lateral spinal curvature ≥ 10° in otherwise healthy children and is the most common pediatric spinal deformity. IS is known to have a strong genetic component; however, the underlying etiology is still largely unknown. Animal models have been used historically to both understand and develop treatments for human disease, including within the context of IS. This intended audience for this review is clinicians in the fields of musculoskeletal surgery and research.

METHODS

In this review article, we synthesize current literature of genetic animal models of IS and introduce considerations for researchers.

RESULTS

Due to complex genetic and unique biomechanical factors (i.e., bipedalism) hypothesized to contribute to IS in humans, scoliosis is a difficult condition to replicate in model organisms.

CONCLUSION

We advocate careful selection of animal models based on the scientific question and introduce gaps and limitations in the current literature. We advocate future research efforts to include animal models with multiple characterized genetic or environmental perturbations to reflect current understanding of the human condition.

Genetic variants associated with the occurrence and progression of adolescent idiopathic scoliosis: a systematic review protocol

BACKGROUND

Adolescent idiopathic scoliosis (AIS) is a structural lateral spinal curvature of ≥ 10° with rotation. Approximately 2-3% of children in most populations are affected with AIS, and this condition is responsible for approximately $1.1 billion in surgical costs to the US healthcare system. Although a genetic factor for AIS has been demonstrated for decades, with multiple potentially contributory loci identified across populations, treatment options have remained limited to bracing and surgery.

METHODS

The databases MEDLINE (via PubMed), Embase, Google Scholar, and Ovid MEDLINE will be searched and limited to articles in English. We will conduct title and abstract, full-text, and data extraction screening through Covidence, followed by data transfer to a custom REDCap database. Quality assessment will be confirmed by multiple reviewers. Studies containing variant-level data (i.e., GWAS, exome sequencing) for AIS subjects and controls will be considered. Outcomes of interest will include presence/absence of AIS, scoliosis curve severity, scoliosis curve progression, and presence/absence of nucleotide-level variants. Analyses will include odds ratios and relative risk assessments, and subgroup analysis (i.e., males vs. females, age groups) may be applied. Quality assessment tools will include GRADE and Q-Genie for genetic studies.

DISCUSSION

In this systematic review, we seek to evaluate the quality of genetic evidence for AIS to better inform research efforts, to ultimately improve the quality of patient care and diagnosis.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration #CRD42021243253.

Severity of Idiopathic Scoliosis Is Associated with Differential Methylation: An Epigenome-Wide Association Study of Monozygotic Twins with Idiopathic Scoliosis

Epigenetic mechanisms may contribute to idiopathic scoliosis (IS). We identified 8 monozygotic twin pairs with IS, 6 discordant (Cobb angle difference > 10°) and 2 concordant (Cobb angle difference ≤ 2°). Genome-wide methylation in blood was measured with the Infinium HumanMethylation EPIC Beadchip. We tested for differences in methylation and methylation variability between discordant twins and tested the association between methylation and curve severity in all twins. Differentially methylated region (DMR) analyses identified gene promoter regions. Methylation at cg12959265 (chr. 7 DPY19L1) was less variable in cases (false discovery rate (FDR) = 0.0791). We identified four probes (false discovery rate, FDR < 0.10); cg02477677 (chr. 17, RARA gene), cg12922161 (chr. 2 LOC150622 gene), cg08826461 (chr. 2), and cg16382077 (chr. 7) associated with curve severity. We identified 57 DMRs where hyper- or hypo-methylation was consistent across the region and 28 DMRs with a consistent association with curve severity. Among DMRs, 21 were correlated with bone methylation. Prioritization of regions based on methylation concordance in bone identified promoter regions for WNT10A (WNT signaling), NPY (regulator of bone and energy homeostasis), and others predicted to be relevant for bone formation/remodeling. These regions may aid in understanding the complex interplay between genetics, environment, and IS.

The role of gene therapy as a valuable treatment modality for multiple spinal pathologies

The world of biomedical research has led to several breakthroughs in the treatment of various spinal pathologies. As we investigate chronic pathologies of the spine, we start to unravel the underlying molecular mechanisms through a careful analysis of mutated genetic sequences. Investigations have led to gene therapy being explored for its potential as a treatment modality. Despite only about 2% of current gene therapy trials being centered for spinal pathologies, spinal diseases are valuable targets in gene therapy administration. Through a comprehensive literature review, our objective is to discuss the molecular mechanisms behind gene therapy for spinal pathologies, the genetic targets, along with the outcomes, success, and possible pitfalls in gene therapy research and administration. The emerging development of robotic technologies and intelligent carriers are recognized as a promising innovative technique for increasing the efficiency of gene therapy and potentially resolving spinal pathologies.

The Susceptibility and Potential Functions of the LBX1 Gene in Adolescent Idiopathic Scoliosis

Genome-wide association studies have identified many susceptibility genes for adolescent idiopathic scoliosis (AIS). However, most of the results are hard to be replicated in multi-ethnic populations. LBX1 is the most promising candidate gene in the etiology of AIS. We aimed to appraise the literature for the association of LBX1 gene polymorphisms with susceptibility and curve progression in AIS. We also reviewed the function of the LBX1 gene in muscle progenitor cell migration and neuronal determination processes. Three susceptibility loci (rs11190870, rs625039, and rs11598564) near the LBX1 gene, as well as another susceptibility locus (rs678741), related to LBX1 regulation, have been successfully verified to have robust associations with AIS in multi-ethnic populations. The LBX1 gene plays an essential role in regulating the migration and proliferation of muscle precursor cells, and it is known to play a role in neuronal determination processes, especially for the fate of somatosensory relay neurons. The LBX1 gene is the most promising candidate gene in AIS susceptibility due to its position and possible functions in muscle progenitor cell migration and neuronal determination processes. The causality between susceptibility loci related to the LBX1 gene and the pathogenesis of AIS deserves to be explored with further integrated genome-wide and epigenome-wide association studies.

From genetics to epigenetics to unravel the etiology of adolescent idiopathic scoliosis

Scoliosis is defined as the three-dimensional (3D) structural deformity of the spine with a radiological lateral Cobb angle (a measure of spinal curvature) of ≥10° that can be caused by congenital, developmental or degenerative problems. However, those cases whose etiology is still unknown, and affect healthy children and adolescents during growth, are the commonest form of spinal deformity, known as adolescent idiopathic scoliosis (AIS). In AIS management, early diagnosis and the accurate prediction of curve progression are most important because they can decrease negative long-term effects of AIS treatment, such as unnecessary bracing, frequent exposure to radiation, as well as saving the high costs of AIS treatment. Despite efforts made to identify a method or technique capable of predicting AIS progression, this challenge still remains unresolved. Genetics and epigenetics, and the application of machine learning and artificial intelligence technologies, open up new avenues to not only clarify AIS etiology, but to also identify potential biomarkers that can substantially improve the clinical management of these patients. This review presents the most relevant biomarkers to help explain the etiopathogenesis of AIS and provide new potential biomarkers to be validated in large clinical trials so they can be finally implemented into clinical settings.

Association of ESRα XbaI A > G, ESRα PvuII T > C and ESRβ AlwNI T > C Polymorphisms with the Risk of Developing Adolescent Idiopathic Scoliosis: A Systematic Review and Genetic Meta-analysis

Several association studies of genes polymorphisms on estrogen receptors-α and β with respect to adolescent idiopathic scoliosis (AIS) have been published in the past two decades. However, the association with AIS, especially among different ethnic subgroups, still remains controversial. Thus, we investigated these inconclusive data by performing a meta-analysis to systematically evaluate the association.

A literature search was conducted in the PubMed, ISI Web of Science, EMBASE, SCOPUS, EBSCO, Cochrane Library, China National Knowledge Infrastructure (CNKI) and Wanfang databases until January 20, 2018. The strength of relationship was assessed using odds ratios (ORs) and 95% confidence intervals (95%CIs).

A total of 12 case–control studies with 4,304 cases of AIS and 3,123 controls met our criteria. The pooled ORs indicated that the ESRα XbaI A > G, ESRα PvuII T > C and ESRβ AlwNI T > C polymorphisms were not significantly associated with the risk of developing AIS in the overall analysis. However, we found a significant association between the ESRα XbaI A > G polymorphism and AIS under the homozygote model (GG versus AA; OR = 1.448, 95%CI: 1.052–1.993; p  = 0.023).

The present meta-analysis suggests that the ESRα XbaI A > G, ESRα PvuII T > C and ESRβ AlwNI T > C polymorphisms may not be associated with the risk of developing AIS in the overall analysis. However, ESRα XbaI A > G might have an influence on the susceptibility to develop AIS among Asians. Considering the limited sample size and ethnicity, further larger studies are needed to provide a more precise estimation of the associations.

Paraspinal muscle ladybird homeobox 1 (LBX1) in adolescent idiopathic scoliosis: a cross-sectional study

BACKGROUND CONTEXT

Adolescent idiopathic scoliosis (AIS) is the leading cause of spinal deformity in adolescents globally. Recent evidence from genome-wide association studies has implicated variants in or near the ladybird homeobox 1 (LBX1) gene, encoding the ladybird homeobox 1 transcription factor, in AIS development. This gene plays a critical role in guiding embryonic neurogenesis and myogenesis and is vital in muscle mass determination. Despite the confirmation of the role for LBX1 gene variants in the development of AIS, the biological basis of LBX1 contribution to AIS remains mostly unknown.

PURPOSE

To investigate the potential role of LBX1 in driving spinal curving, curve laterality, and progression through muscle-based mechanisms in AIS patients by analyzing its gene and protein expression.

STUDY DESIGN

This is a cross-sectional study using clinical data and biological samples from the Immunometabolic CONnections to Scoliosis study (ICONS study).

PATIENT SAMPLE

Twenty-five patients with AIS provided informed consent. Paraspinal muscle biopsies from the maximal points of concavity and convexity for gene expression and protein analysis were obtained at the start of corrective spinal surgery.

OUTCOME MEASURES

The outcome measures included the detection of paraspinal muscle LBX1 mRNA abundance and LBX1 protein expression and the correlation of the latter with age, sex, and curve severity.

METHODS

The measurement of mRNA abundance was done using quantitative real-time polymerase chain reaction (qRT-PCR). Additionally, protein lysates from the biopsied muscle samples were probed with a monoclonal LBX1 antibody to compare the muscle protein levels on either side of the scoliotic curve by western blot. This study received funding from the Division of Orthopedics, Department of Surgery, McMaster University, Hamilton, Ontario, Canada ($39,900 CAN for 2 years). The authors have no conflicts of interest to disclose.

RESULTS

LBX1 mRNA abundance (concave 2.98±0.87, convex 3.40±1.10, p value 0.73) and protein expression (concave 1.20±0.13, convex 1.21±0.10, p value 0.43) were detected on both sides of the scoliotic curve at equivalent levels. The expression of LBX1 protein did not correlate with age (concave: correlation coefficient 0.32, p value 0.12; convex: correlation coefficient 0.08, p value 0.69), sex (concave: correlation coefficient -0.03, p value 0.08; convex: correlation coefficient 0.07, p value 0.72), or the severity of spinal curving measured using the Cobb angle (concave: correlation coefficient -0.16, p value 0.45; convex: correlation coefficient -0.08, p value 0.69).

CONCLUSIONS

LBX1 is expressed in erector spinae muscles, and its levels are equal in muscles on both sides of the scoliotic curve in AIS. The expression of LBX1 on the convex and concave sides of the scoliotic curve did not correlate with age, sex, or the severity of spinal curving. The molecular mechanisms by which LBX1contributes to the development and propagation of AIS need to be explored further in muscle and other tissues.

Positive association between a polymorphic locus near the LBX1 gene and predisposition of idiopathic scoliosis in Southeastern European population

Idiopathic scoliosis (IS) is a common medical condition in children, characterized by three-dimensional spinal curve and strong evidence of genetic predisposition. The purpose of the present case-control study is to examine the association between the polymorphic variant rs11190870 (T/C), near the LBX1 gene, and IS predisposition in distinct subgroups based on age at onset, family history and gender. A total of 127 IS patients and 254 unrelated controls of Southeastern European descent were recruited. The genotyping was carried out by TaqMan real-time amplification technology. The results were analyzed by the Pearson's Chi-squared Test and the Fisher's Exact Test with a value of p less than 0.05 as statistically significant. The T allele and homozygous TT genotype were associated with a greater incidence of IS. Our results suggest that there is a genetic association with IS in adolescents, familial and non-familial cases, and in females. Larger case-control studies are necessary to examine the genetic factors of IS/AIS etiology in infants, juveniles and males. In conclusion, the molecular genetic identification of diagnostic and prognostic molecular markers would make an early treatment including minimally invasive procedures possible.

Association between ladybird homeobox 1 gene polymorphisms and adolescent idiopathic scoliosis: A MOOSE-compliant meta-analysis

The Ladybird Homeobox 1 (LBX1) gene has been implicated in the etiology of adolescent idiopathic scoliosis (AIS). The association between LBX1 gene polymorphisms and AIS has been investigated in several studies. However, these findings have yield contradictory results rather than conclusive evidence.This study is to provide a meta-analysis of the published case-control studies on the association between LBX1 gene polymorphisms and AIS in Asian and Caucasian populations.This meta-analysis conformed to the Meta-Analysis of Observational Studies in Epidemiology (MOOSE) guidelines. We conducted a literature research on PubMed, Embase, Web of Science, and Cochrane Library until February 10, 2018. We included all case-control or cohort studies about association between LBX1 gene polymorphisms and AIS. The Risk Of Bias In Non-randomised Studies-of Interventions and Critical Appraisal Skills Programme were used to evaluate the risk of bias and study quality. We assessed the strength of association by pooled odds ratios (ORs) and 95% confidence intervals (CIs) in all genetic models under a fixed-effect model or random-effect model. We further performed subgroup analysis by ethnicity and sex. Sensitivity analysis and publication bias were also undertaken.A total of 10 studies (11,411 cases and 26,609 controls) were included in this meta-analysis. The pooled results showed a statistically significant association between LBX1 gene polymorphisms and AIS (for rs11190870, T vs C, OR = 1.54, 95% CI = 1.48-1.61, P < .00001; for rs625039, G vs A, OR = 1.50, 95% CI: 1.38-1.62; P < .00001; for rs678741, G vs A, OR = 0.74, 95% CI: 0.63-0.86; P < .0001; for rs11598564, G vs A, OR = 1.41, 95% CI: 1.31-1.51; P < .0001). For stratified analyses by ethnicity and sex, robust significant associations were detected in Asian and Caucasian populations, and in women and men under all genetic models.T allele of rs11190870 and G alleles of rs625039 and rs11598564 represent risk factors for AIS, but G allele of rs678741 may play a protective role in the occurrence of AIS. Further research is needed to confirm this finding and to understand its implications.

A multi-ethnic meta-analysis confirms the association of rs6570507 with adolescent idiopathic scoliosis

Adolescent idiopathic scoliosis (AIS) is the most common type of spinal deformity and has a significant genetic background. Genome-wide association studies (GWASs) identified several susceptibility loci associated with AIS. Among them is a locus on chromosome 6q24.1 that we identified by a GWAS in a Japanese cohort. The locus is represented by rs6570507 located within GPR126. To ensure the association of rs6570507 with AIS, we conducted a meta-analysis using eight cohorts from East Asia, Northern Europe and USA. The analysis included a total of 6,873 cases and 38,916 controls and yielded significant association (combined P = 2.95 × 10^-20; odds ratio = 1.22), providing convincing evidence of the worldwide association between rs6570507 and AIS susceptibility. In silico analyses strongly suggested that GPR126 is a susceptibility gene at this locus.

Idiopathic Scoliosis Families Highlight Actin-Based and Microtubule-Based Cellular Projections and Extracellular Matrix in Disease Etiology

Idiopathic scoliosis (IS) is a structural lateral spinal curvature of ≥10° that affects up to 3% of otherwise healthy children and can lead to life-long problems in severe cases. It is well-established that IS is a genetic disorder. Previous studies have identified genes that may contribute to the IS phenotype, but the overall genetic etiology of IS is not well understood. We used exome sequencing to study five multigenerational families with IS. Bioinformatic analyses identified unique and low frequency variants (minor allele frequency ≤5%) that were present in all sequenced members of the family. Across the five families, we identified a total of 270 variants with predicted functional consequences in 246 genes, and found that eight genes were shared by two families. We performed GO term enrichment analyses, with the hypothesis that certain functional annotations or pathways would be enriched in the 246 genes identified in our IS families. Using three complementary programs to complete these analyses, we identified enriched categories that include stereocilia and other actin-based cellular projections, cilia and other microtubule-based cellular projections, and the extracellular matrix (ECM). Our results suggest that there are multiple paths to IS and provide a foundation for future studies of IS pathogenesis.

Circulating miRNAs as diagnostic biomarkers for adolescent idiopathic scoliosis

The aetiology of adolescent idiopathic scoliosis (AIS) has been linked to many factors, such as asymmetric growth, neuromuscular condition, bone strength and genetic background. Recently, epigenetic factors have been proposed as contributors of AIS physiopathology, but information about the molecular mechanisms and pathways involved is scarce. Regarding epigenetic factors, microRNAs (miRNAs) are molecules that contribute to gene expression modulation by regulating important cellular pathways. We herein used Next-Generation Sequencing to discover a series of circulating miRNAs detected in the blood samples of AIS patients, which yielded a unique miRNA biomarker signature that diagnoses AIS with high sensitivity and specificity. We propose that these miRNAs participate in the epigenetic control of signalling pathways by regulating osteoblast and osteoclast differentiation, thus modulating the genetic background of AIS patients. Our study yielded two relevant results: 1) evidence for the deregulated miRNAs that participate in osteoblast/osteoclast differentiation mechanisms in AIS; 2) this miRNA-signature can be potentially used as a clinical tool for molecular AIS diagnosis. Using miRNAs as biomarkers for AIS diagnostics is especially relevant since miRNAs can serve for early diagnoses and for evaluating the positive effects of applied therapies to therefore reduce the need of high-risk surgical interventions.

Association of vitamin D receptor BsmI rs1544410 and ApaI rs7975232 polymorphisms with susceptibility to adolescent idiopathic scoliosis: A systematic review and meta-analysis

BACKGROUND

AIS is the most common spinal deformity disease, yet its etiology remains uncertain. Significant associations have been found between AIS risk and vitamin D receptor (VDR) gene polymorphisms; however, some of these results are controversial. The aim of this study was to determine whether VDR BsmI rs1544410 and ApaI rs7975232 polymorphisms are correlated with AIS.

METHODS

Databases, including PubMed, EMBASE, Web of Science, the Cochrane Library, the Chinese Biomedical Literature Database, and the Wanfang Database, were systematically searched, and eligible case-control studies that explored the association of VDR (BsmI and ApaI) and the susceptibility to AIS were selected. The pooled odds ratio (OR) with 95% confidence interval (95% CI) was calculated to assess the associations, and subgroup meta-analyses were performed according to the ethnicity of the study population.

RESULTS

A total of 5 studies with 717 cases and 554 controls fulfilled the inclusion criteria after assessment by 2 reviewers. Generally, significant correlations were found between the BsmI polymorphism and AIS risk in overall populations and in Asian populations (overall population: B vs b: OR = 2.12, 95% CI = 1.21-3.75, P = .009; BB vs bb: OR = 3.38, 95% CI = 1.08-10.57, P = .036; Bb vs bb: OR = 2.50, 95% CI = 1.29-4.82, P = .006; BB/Bb vs bb: OR = 2.71, 95% CI = 1.31-5.63, P = .007; Asian population: B vs b: OR = 2.42, 95% CI = 1.27-4.61, P = .007; BB vs bb: OR = 4.09, 95% CI = 1.03-16.22, P = .045; Bb vs bb: OR =  2.94, 95% CI = 1.42-6.10, P = .004; BB/Bb vs bb: OR = 3.23, 95% CI = 1.42-7.35, P = .005). There was no significant association observed in Caucasian populations (all P > .05). With regard to the ApaI polymorphism, we found that it significantly decreased the risk of AIS (Aa vs AA: OR = 0.43, 95% CI = 0.24-0.77, P = .004; Aa/aa vs AA: OR = 0.52, 95% CI = 0.30-0.91, P = .023); however, we could not draw a definitive conclusion for Caucasian populations, as no studies have been conducted in this group to determine the role of the VDR ApaI polymorphism in AIS etiology and development.

CONCLUSION

VDR BsmI was significantly associated with AIS susceptibility in the overall and Asian populations, while the VDR ApaI polymorphism only played a key role in AIS etiology and development in Asian populations.

Etiological Theories of Adolescent Idiopathic Scoliosis: Past and Present

Adolescent idiopathic scoliosis is one of the most common spinal deformities, yet its cause is unknown. Various theories look to biomechanical, neuromuscular, genetic, and environmental origins, yet our understanding of scoliosis etiology is still limited. Determining the cause of a disease is crucial to developing the most effective treatment. Associations made with scoliosis do not necessarily point to causality, and it is difficult to determine whether said associations are primary (playing a role in development) or secondary (develop as a result of scoliosis). Scoliosis is a complex condition with highly variable expression, even among family members, and likely has many causes. These causes could be similar among homogenous groups of AIS patients, or they could be individual. Here, we review the most prevalent theories of scoliosis etiology and recent trends in research.